Pet peeve: empty .notdef character.

I just spent some time browsing fonts on typekit and was surprised by the number of fonts I came across which had a blank .notdef character. What's worse, a few had blank, zero-width .notdef characters.

I just thought I’d use this forum to urge people to please include some sort of glyph in this slot. Be creative or just use a simple square. Just please don't leave it blank!